Problem configuring double framebuffer and 24bpp on STM32F769I-DISCO

Hi,

​

A minimal example would be nice :grinning_face_with_sweat: so that I/we can try to replicate it.

​

/Romain

Hi, i couldnt figure out a solution for this problem in the last week. Does anybody have suggestions what i could try to change in my configuration? I attached a minimal example in my previous post.

Manuel

Hello MGass.1,

I've looked into your project and it's almost correct except that in TouchGFXHAL.cpp, it's still using the 16bpp "way" of refreshing your screen. In 16 bpp, the screen is splitted in 4 and your refresh 200 pixel at a time, whereas in 24 bpp, it should refresh the 448 pixels.

In the HAL_DSI_TearingEffectCallback() funtion, there's commented code that you need to use instead of what it's currently implemented (because originally designed for 16bpp).

2 things to change :

In HAL_DSI_TearingEffectCallback()

 LCD_SetUpdateRegionLeft();
//LCD_SetUpdateRegion(updateRegion);

In HAL_DSI_EndOfRefreshCallback(), use :

void HAL_DSI_EndOfRefreshCallback(DSI_HandleTypeDef *hdsi)
 {
 if (displayRefreshing)
 {
 if (updateRegion == 0)
 {
 // If we transferred the left half, also transfer right half.
 __HAL_DSI_WRAPPER_DISABLE(hdsi);
 LTDC_LAYER(&hltdc, 0)->CFBAR = ((uint32_t)currFbBase) + 448 * 3;
 uint16_t ADJUSTED_WIDTH = 384; //64-byte aligned width
 uint16_t REAL_WIDTH = 384 - 32; //we only actually have this amount of pixels on display
 LTDC->AWCR = ((ADJUSTED_WIDTH + 2) << 16) | 0x1E2; //adj
 LTDC->TWCR = ((REAL_WIDTH + 2 + 1 - 1) << 16) | 0x1E3;
 LTDC_LAYER(&hltdc, 0)->WHPCR = ((REAL_WIDTH + 2) << 16) | 3;
 LTDC_LAYER(&hltdc, 0)->CFBLR = ((832 * 3) << 16) | ((REAL_WIDTH) * 3 + 3);
 __HAL_LTDC_RELOAD_IMMEDIATE_CONFIG(&hltdc);
 LCD_SetUpdateRegionRight(); //Set display column to 448-799
 __HAL_DSI_WRAPPER_ENABLE(hdsi);
 updateRegion = 1;
 
 HAL_DSI_Refresh(hdsi);
 }
 else
 {
 // Otherwise we are done refreshing.
 
 __HAL_DSI_WRAPPER_DISABLE(hdsi);
 LTDC_LAYER(&hltdc, 0)->CFBAR = (uint32_t)currFbBase;
 uint16_t WIDTH = 448;
 LTDC->AWCR = ((WIDTH + 2) << 16) | 0x1E2;
 LTDC->TWCR = ((WIDTH + 2 + 1) << 16) | 0x1E3;
 LTDC_LAYER(&hltdc, 0)->WHPCR = ((WIDTH + 2) << 16) | 3;
 LTDC_LAYER(&hltdc, 0)->CFBLR = (((832 * 3) << 16) | ((WIDTH * 3) + 3));
 __HAL_LTDC_RELOAD_IMMEDIATE_CONFIG(&hltdc);
 LCD_SetUpdateRegionLeft(); //Set display column to 0-447
 __HAL_DSI_WRAPPER_ENABLE(hdsi);
 GPIO::clear(GPIO::VSYNC_FREQ);
 
 // Turn on display if not already active
 LCD_ReqEnable();
 
 displayRefreshing = false;
 if (HAL::getInstance())
 {
 // Signal to the framework that display update has finished.
 HAL::getInstance()->frontPorchEntered();
 }
 }
 }
 }

With these changes it should be working fine :)

/Osman